Soft silicone hydrogel contact lenses are increasingly becoming popular because of their high oxygen permeability and comfort. But, a silicone hydrogel material typically has a surface, or at least some areas of its surface, which is hydrophobic (non-wettable) and susceptible to adsorbing lipids or proteins from the ocular environment and may adhere to the eye. Thus, a silicone hydrogel contact lens will generally require a surface modification.
A known approach for modifying the hydrophilicity of a relatively hydrophobic contact lens material is through the use of a plasma treatment, for example, commercial lenses such as Focus NIGHT & DAY™ and O2OPTIX™ (CIBA VISION), and PUREVISION™ (Bausch & Lomb) utilize this approach in their production processes. Advantages of a plasma coating, such as, e.g., those may be found with Focus NIGHT & DAY™, are its durability, relatively high hydrophilicity/wettability), and low susceptibility to lipid and protein deposition and adsorption. But, plasma treatment of silicone hydrogel contact lenses may not be cost effective, because the preformed contact lenses must typically be dried before plasma treatment and because of relative high capital investment associated with plasma treatment equipment.
Various other approaches are proposed and/or used for modifying the surface hydrophilicity of a silicone hydrogel contact lens. Examples of such approaches include: incorporation of wetting agents (hydrophilic polymers) into a lens formulation for making the silicone hydrogel contact lens (see, e.g., U.S. Pat. Nos. 6,367,929, 6,822,016, 7,052,131, and 7,249,848); a layer-by-layer (LbL) polyionic material deposition technique (see, e.g., U.S. Pat. Nos. 6,451,871; 6,719,929; 6,793,973; 6,884,457; 6,896,926; 6,926,965; 6,940,580; and 7,297,725, and U.S. Pat. Appl. Pub. Nos. 2007/0229758A1; 2008/0174035A1 and 2008/0152800A1); crosslinking of LbL coatings on contact lenses has been proposed in commonly-owned copending US pat. Appl. pub. Nos. 2008/0226922 A1 and 2009/0186229 A1; and attachment of hydrophilic polymers onto contact lenses according to various mechanisms (see for example, U.S. Pat. Nos. 6,099,122, 6,436,481, 6,440,571, 6,447,920, 6,465,056, 6,521,352, 6,586,038, 6,623,747, 6,730,366, 6,734,321, 6,835,410, 6,878,399, 6,923,978, 6,440,571, and 6,500,481, US Pat. Appl. Pub. Nos. 2009/0145086 A1, 2009/0145091A1, 2008/0142038A1, and 2007/0122540A1). Although those techniques can be used in rendering a silicone hydrogel material wettable, there are some shortcomings in those techniques. For example, wetting agents may impart haziness to the resultant lenses because of their incompatibility with other silicone components in the lens formulation and may not provide a durable hydrophilic surface for extended wear purposes. LbL coatings may not be as durable as plasma coatings and may have relatively high densities of surface charges; which may interfere with contact lens cleaning and disinfecting solutions. Crosslinked LbL coatings may have a hydrophilicity and/or wettability inferior than original LbL coatings (prior to crosslinking) and still have relative high densities of surface charges. In addition, they may not be cost-effective and/or time-efficient for implementation in a mass production environment, because they typically require relatively long time and/or involve laborious, multiple steps to obtain a hydrophilic coating.
Recently, a new cost-effective approach has been described in U.S. Pat. No. 8,529,057 (herein incorporated by reference in its entirety) for applying a non-silicone hydrogel coating onto a silicone hydrogel contact lens, involving the extraction of the silicone hydrogel contact lens with an organic solvent, contacting of the extracted silicone hydrogel contact lens with an organic solvent-based coating solution to form a stable, interpenetrating base coating on a silicone hydrogel contact lens, rinsing of the silicone hydrogel contact lens with a mixture of water and an organic solvent, and covalently attaching of a partially-crosslinked hydrophilic polymeric material onto the base coating directly in a lens package during autoclave. Although this new approach can provide silicone hydrogel contact lenses with durable hydrophilic coatings thereon, it may not be environmentally friendly manufacturing process because it involves use of organic solvents in lens processing steps after the lens molding step.
Therefore, there is still a need for new method for manufacturing silicone hydrogel contact lenses with a stable, lubricious coating thereon in an environmentally-friendly manner.